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Efeito do pó de vidro na mitigação da reação álcali-sílica de compósitos cimentícios de alto desempenho
(Universidade Federal de São Carlos, 2019-11-06) Freitas, Taís Oliveira Gonçalves; Ferreira, Fernanda Giannotti da Silva; https://lattes.cnpq.br/0329487394818763; https://lattes.cnpq.br/8924772434348795
For some years researches has been adressing the replacement of part of the cement used in concrete and mortars with alternative materials such as ground glass powder. This alternative reduces 〖CO〗_2, emissions since it’s used a smaller portion of concrete. In order for this substitution to be considered viable and applicable on the market, several factors and possible problems that this incorporation may result should be examined. One of the problems that can compromise the durability of concrete is the Alkali-Aggregate Reaction. This reaction causes expansion and fissure of concrete elements, by the chemical reaction between the reactive aggregate, alkaline concrete ions and hydroxyl ions, in the presence of moisture. So, this work aims to evaluate the effect of the incorporation of ground glass powder into cementied composites in the Alkali-Aggregate Reaction. Cementious composites were made with CPV cement, active silica, additives, sand with a maximum dimension of 1.2 mm, water (water/cement ratio of 0.18) and incorporation of glass powder in the contents of 0%,10%,20%,30% and 50% in volumetric replacement to cement. Tests were performed to characterize cementitious composites, axial compression resistance, capillarity water absorption, tensile strength by diametric compression, tensile strength in flexion, static elasticity module and dynamic. Expansion tests were performed in mortar bars by the accelerated method in order to evaluate the mitigation of expansions. The results show that the incorporation of glass powder did not interfere in the workability of the mixture in the fresh state, and reduced the air content incorporated into the mixture. There was an improvement in the mechanical and physical properties of cementitious composites from 28 days, such as a decrease in water absorption by capillarity and resistance to axial compression, obtaining the highest value for composite with 30% of glass powder in 129.03 MPa and high elasticity modules, in order of 45 to 50 GPa, characteristics of high performance concrete. Concerning the results found for cementitious composites with incorporation of glass powder, they reached values close to those of the reference material. Already for the specific tests of Alkali-Silica Reaction, it is noted that the contents of 10 and 20% of glass powder incorporation increased expansions in the mortar bars studied and the contents of 30 and 50% decreased to expansions, reaching dimensional variations close to 0%. Therefore, the behavior in the face of the Alkali-Silica Reaction varied according to the glass powder content of the mixtures. It was found that 30 and 50% of incorporation are the optimal substitution levels in relation to the alkali-silica reaction.
Compósitos de alginato como material inteligente, modulação de solubilidade e objeto de ensino
(Universidade Federal de São Carlos, 2019-11-06) Cacuro, Thiago Aguiar; Duek, Eliana Aparecida de Rezende; https://lattes.cnpq.br/4147198882685212; Waldman, Walter Ruggeri; https://lattes.cnpq.br/0616238673458322; https://lattes.cnpq.br/4782607993099360
Alginate is a nontoxic, biocompatible polymer, that is easily obtainable. It can form gels through crosslinking when in contact with bivalent metal ions (ionic alginate gel) or through intermolecular bonds by exposure to a pH smaller than its monomers pKa (acid alginate gel). In the first part of this work, coreshell composites in the form of beads, were developed. These beads are composed of a mixture of acid and ionic alginate gel, with a novel phenomenon to alginate beads, those beads open, when exposed to neutral pH. The composites were characterized and their application as a pH-controlled release device was tested. In the controlled release tests, the methylene blue dye was used as a model molecule. In the second part of this work, the modulation of sodium alginate solubility, was made by the addition of an ester group in the chemical structure of the alginate. After esterification, the ester group was functionalized by the addition of a thiol group as proof of concept. The addition of the ether group promoted a modulation of the alginate solubility, making it soluble in organic solvents. In the last part of this work, polymers were used as a teaching object. Practical experiments using polymers were planned and applied with students, exposing the practical class protocol, its application with graduate students and the pedagogical results of these experiments. The aim is to evaluate the effectiveness in the acquisition of knowledge and applicability in teaching of those protocols.
Caracterização das nascentes e ecossistemas dependentes das águas subterrâneas: estudo de caso no município de Analândia-SP
(Universidade Federal de São Carlos, 2019-11-06) Luiz, Junio da Silva; Ferreira, Marcilene Dantas; https://lattes.cnpq.br/1557946634389893; https://lattes.cnpq.br/8870880968252584
The analysis of springs by models to geomorphological aspects and by studies of Groundwater Dependent Ecosystems (GDEs) are good tools to manage water resources. However, there is a lack of information, both on the classification of springs and on the GDEs. The objective of this work is to provide subsidies to increase the understanding about the themes. For this, a field study was carried out in the city of Analândia-SP, and from 28 springs several aspects were addressed regarding the classification of springs and the GDEs, using the models already available in the literature and trying to understand the relationship with the springs found in the field. Springs were found that fit 06 geomorphological models of springs and a range of information related to GDEs. It was possible, from the results, to see that the models adopted and the GDEs compression can be two useful tools for decision making.
Modificação das propriedades estruturais, morfológicas e ópticas do Ag3PO4 e Ag2-2xZnxWO4(0≤ x ≤ 0.25)
(Universidade Federal de São Carlos, 2019-11-06) Santos, Clayane Carvalho dos; Longo, Elson; https://lattes.cnpq.br/9848311210578810; https://lattes.cnpq.br/7029593164814773
Phosphates and tungstates are important compounds and known mainly for their photocatalytic and photoluminescent properties. The present work proposes a study of the structural, morphological and photoluminescent properties of the materials: Ag3PO4 electron beam irradiated and femtosecond laser, and Ag2-2xZnxWO4 (0≤ x ≤ 0.25) modified with different concentrations of Zn+ obtained by the method of co-precipitation. The obtained phases were characterized by X-ray diffraction, Raman scattering spectroscopy, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and photoluminescence measurements. The main results investigated for the irradiated Ag3PO4 crystals show that XRD diffraction data show that the patterns for the non-irradiated and similar electron-irradiated samples, while the femtosecond laser-irradiated sample has a higher resolution XRD pattern, low, showing a higher structural disturbance at long range. For the Raman and Rietveld Spectra they show that both [PO4] and [AgO4] are distorted clusters, being the Ag-O bonds of agglomerates [AgO4] more labile than the P-O bonds of clusters [PO4]. In addition, a distinct growth and size mechanism was observed in the production of metallic Ag. For Ag2WO4, the results showed that the increase of Zn concentration in the microcrystals in the α-Ag2WO4 host matrix caused a morphological transformation and a shift of the electronic and optical properties. And regarding the photuluminescent properties of the α-Ag2WO4 and α-Ag2-2xZnxWO4 microcrystals are explained by the effects of distortions and oxygen vacancies (V_O^x) on clusters [WO6] and [AgOy] (y = 2, 4, 6 and 7) respectively causing a redshift.